Aspergillus niger KKS, a laboratory isolate, has previously been shown to have considerable cellulolytic and hemicellulolytic activity when grown on rice-straw In the present work, we have compared the activities, yields and productivities of cellulase and xylanase obtained in shake-flask, stirred-tank bubble-column, and air-lift reactors. In general, better yield and productivity were shown in a bubble-column and an external-loop air-lift than in the stirred-tank reactor The highest yield and productivity of cellulase were 84 FPA IU/g and 9.7 FPA IU/l.h, obtained by fed-batch mode in the bubble-column and in the stirred-tank reactor respectively. In the case of beta-glucosidase, the highest yield and productivity were 370 U/g and 26 U/l.h in an external-loop air-lift reactor. For xylanase, the highest yield was 9100 U/g in a bubble-column, and the highest productivity was 823 U/l.h in an external-loop air-lift reactor with fed-batch mode. (C) 1997 Elsevier Science Ltd.